COLICS IN HORSES. 
225 
brane of the intestine itself. This first portion of the intestine pos¬ 
sesses a vascular and nervous organization perfectly in proportion 
to the important functions belonging to it. This accounts for the 
delicate sensitiveness of this viscera, and especially of its mucous 
membrane, while its mobility explains the pathological modifica¬ 
tions to which it is subject, and its abundant vascularity accounts 
also for the multiplicity of the congestive and inflammatory pro¬ 
cesses to which it is liable. 
The large intestine has its special reservoirs in the coecum and 
the large colon, in which is contained and completed the elabora¬ 
tion of the digestive fluids. It serves, especially the coecum, as a 
second stomach, in which the remainder of the non-absorbed liquid 
is terminated. From this point the ingested aliments, deprived at 
last, more or less, of their soluble and assimilable principles, 
are concentrated and taken on their travels through these viscera 
in a more or less developed consistency. These alimentary 
matters, thus modified, reach the small colon and there are sub¬ 
divided and pass to the rectum, to be expelled by the final aid of 
defecation. 
Such, in a few words, is the functions of this apparatus. By 
its normal performance, the soluble portion, or that which has 
become so, of the food, has been absorbed and passed into the 
circulatory system, while the other and useless portion is thrown 
back in the external world where it comes from. 
This canal, in which are thus collected and manipulated, as*in 
an immense laboratory, the great physico-chemical materials and 
operations of digestion, is composed of three superposed mem¬ 
branes: 1. A serous envelope, dependent on the peritoneum, and 
possessed of all the properties of this form of membrane. 2. A 
muscular tissue, composed of unstriated, contractile fibres, whose 
excitation is under the influence of the pneumo-gastric and great 
sympathetic nerves. It forms what we call the gastro-intestinal 
muscle. This, by its peristaltic and anti-peristaltic contractions, 
forms the active agent in the ingestion of the solid, liquid and 
gaseous substances that travel through it. 3. A mucous mem¬ 
brane, constituting over almost its entire surface an extensive ap¬ 
paratus of secretion and absorption, whose abnormal functions 
